Passenger restraint devices have been known which actuate to restrain a passenger on the basis of pre-crash sensing. For example in a passenger restraint device disclosed in JP-A-9-175327, a seat belt reeling-in action is started when a time to a crash (available time before crash), which is the value obtained by dividing a distance to a crash object by a present value of relative speed, has become less than a predetermined threshold time set to at least be longer than a minimum time below which crash avoidance is impossible. In other words, this vehicle passenger restraint device starts a seat belt reeling-in operation to restrain the passenger at a point in time (actuation start time) ahead of an estimated crash time by the above-mentioned predetermined threshold time.
However, with this vehicle passenger restraint device, there has been the problem that when the actual crash time deviates from the estimated crash time as a result of a vehicle-driving operation for avoiding crash of the own vehicle before the crash, the vehicle passenger restraint device cannot be made to actuate with suitable timing.
Specifically, when as a result of such a vehicle-driving operation the crash time becomes earlier, there is a possibility of the crash occurring before the seat belt has been reeled in sufficiently (before a satisfactory tension has been applied to the seat belt). Conversely, when a tension is applied to the seat belt as early as possible with ample allowance to prevent this kind of problem, reeling-in of the seat belt occurs frequently in cases where it is possible to avoid a crash easily by a subsequent vehicle-driving operation. That is, in seat belt reeling-in of related art, because in the estimation of the estimated crash time the vehicle-driving operation has not been taken into account at all, there has been the possibility of this problem arising.
And, in a passenger restraint device of this kind, after the estimated crash time has passed it is desirable for the seat belt to be slackened, irrespective of whether or not a crash took place. To this end, after a fixed time (actuation time) has elapsed from the actuation start time, the seat belt reeling-in device is ordered to perform a slackening operation.
However, because a time which goes back by a predetermined threshold time from the estimated crash time is set as the actuation start time, when due to a change in the speed of the own vehicle accompanying a steering maneuver the actual crash time is later than the estimated crash time, there is a possibility of the seat belt slackening operation being started before the actual crash time. This problem can be solved by the time from the estimated crash time to the slackening start time being set long. However, with this kind of solution there is the possibility of giving the passenger a disconcerting feeling.
And, a seat belt reeling-in device (passenger restraint device) of related art is set so that reeling-in is always executed with a fixed actuation rise time (current pattern) However, in cases such as that of an accident caused by a vehicle suddenly pulling out, it is conceivable that at the stage at which the danger of an accident is recognized and an estimated crash time is calculated, already it may not be possible to secure an actuation rise time adequate for a sufficient tension to be applied to the seat belt. In cases like this, it is desirable for the motor of the seat belt reeling-in device to be operated at full load and for reeling-in of the seat belt to be carried out at maximum speed. However, when reeling-in is always carried out at maximum speed, problems such as the passenger being given a disconcerting feeling and the consumed electrical power increasing arise.
Also, in a seat belt reeling-in device (passenger restraint device) of related art, a fixed tension is applied to the seat belt at all times after reeling-in. However, in practice, crash danger situations in which seat belt reeling-in is carried out include various cases, such as for example situations not thought to be very dangerous, situations in which the driver can avoid a crash easily, emergency situations in which a crash has already become unavoidable and so on. Therefore, in the related art, when as the fixed tension a maximum tension is always applied after reeling-in of the seat belt, there will be cases when the driver is given a disconcerting feeling. On the other hand, when the tension applied to the seat belt after reeling-in is made lighter, there is the problem that the necessary passenger protection is not obtained.
This invention was made in view of the problems discussed above, and it is an object of the invention to provide a vehicle safety device with which it is possible to realize an optimal passenger protection action while keeping disconcerting of the passenger to a minimum by suitably altering the passenger protection timing and passenger protection operation in correspondence with changes in the traveling state of the vehicle.